The present invention relates to industrial vehicles including forklift trucks and the like that are operated from liquid fuel contained within fuel tanks on the vehicles. More particularly, the present invention relates to measuring pressurized liquid fuel levels in fuel tanks used on such vehicles and indicating to operators of the vehicles when the tanks are approaching empty and approximately how much operating time remains. A common liquid fuel is liquid propane (LP) which is used to power many forklift trucks. Accordingly, the invention will be described with reference to forklift trucks which use LP as fuel. It is noted however, that the present invention is equally applicable to other industrial vehicles that use liquid fuel and liquid fuels other than LP including, for example, natural gas (NG). For ease of description, “propane,” “LP” or “fuel” will be used herein to refer to all currently available liquid fuels and liquid fuels that may become available in the future.
Knowing when an energy supply is nearing exhaustion and the corresponding operating time remaining is important to operators since a vehicle may be operated well away from an area where fuel can be replenished. Typically, industrial vehicles which exhaust their fuel supplies are difficult if not impossible to move and, if not near or in a refueling area, it may be difficult and time-consuming to refuel them. Accordingly, the remaining fuel and run time is important information particularly to newer, less experienced operators.